Chinese languages

I think I have understood it. So I offer some embarassing corrections:
1) actually I think that word is jyun4 kwai1
2) in characters it is 圓規, am I mistaken?
3) that's the V-shaped object you will use to draw a circle?
sorry to clog the board

Not so sure if I have the tones right, but can anyone out there figure out the word I mean? thanks. (if you're using Lau/Yale romanization, that first syllable "jyun," you'd spell it as "yuen" or "yuhn" respectively)